1. Field of the Invention
This invention relates to heterocyclic multifunctional amine adducts, methods of preparing the same, curable compositions containing the same and methods of curing the same.
2. Description of the Prior Art
Polymerized resins are employed for many commercial and military applications. These compositions provide lightweight products which have a high strength to weight ratio and good durability. Polymerized compositions are employed for many end uses which include molding compounds, adhesives, laminates made by bonding layers of impregnated reinforcement together and other such molded products. Particularly important is the use of polymerized epoxy resin in combination with reinforcements for aircraft and aerospace applications. These specific articles generally require very smooth surfaces combined with high temperature strength and resistance to stress fatigue. Applications include aircraft tail assemblies, leading edges and fairings. Polyepoxides, phenolics, isocyanates and bismaleimides represent examples of polymers which are cured by combining them with catalysts or hardeners to yield cured or cross-linked compositions. Typical hardeners or cross-linking agents which cure epoxy prepolymers are aliphatic and aromatic polyamines. Smith et al, U.S. Pat. No. 3,032,526, discloses the curing of a glycidyl polyether of a dihydric phenol with the reaction product of m-phenylenediamine and a dialkyl ketone. Ramos, U.S. Pat. No. 3,398,211, discloses synthetic resins derived from diglycidylethers of polyhydric alcohols interacting with diamines or hydroquinones and 1,4-cyclohexadiene dioxide. Labana et al, U.S. Pat. No. 3,714,120, discloses accelerators which are used to catalyze the curing of bisphenol A-epoxy type resins by aromatic diamines. Montesano, U.S. Pat. No. 3,316,191, discloses the curing of epoxy resins with tertiary amines in the presence of converters such as dodecenyl succinic anhydride. Kehr, U.S. Pat. No. 3,171,830, discloses a cross-linking process for solid olefin polymers containing carbonyl groups by subjecting said polymers to the action of hydrazine or a polyamine compound. Suzuki et al, U.S. Pat. No. 3,950,451, discloses a hardenable composition of an epoxy compound and a hardener produced by coupling a phenol, a diamine, formaldehyde or a functional derivative thereof and an alkylphenol. Current technology uses diamino diphenyl sulfone which is commonly referred to as DDS for curing epoxy resins to yield good mechanical properties of the cured part at elevated temperatures, e.g., Chemical Abstracts 89: 44579 m (Aponyi et al, Natl. SAMPE Symp. Exhib. 1978, 23, 479-89). However, sulfones in general, result in a cross-linked composition which has poor wet strength after being subjected to a wet or high humidity water environment.
Also, the cured compositions utilizing sulfones as the cross-linking agent have brittle failure characteristics or what is commonly described as a lack of toughness. This problem has been overcome to some extent by the addition of plasticizers, flexibilizers or elastomers which when admixed with the polymerizing resin increase fatigue resistance or brittle failure to some degree. These additives when used in combination with DDS cross-linking agent and a N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl methane represent the current state of the art. A need therefore continues to exist for curative agents which will yield materials having excellent physical and mechanical properties.